Development process for lith-type emulsion with n-vinyl 2-pyrrolidone polymer

ABSTRACT

A process for developing a light-sensitive silver halide photographic material containing a negative silver halide emulsion layer of the lith-type comprising the steps of developing the material in the presence of an N-vinyl-2pyrrolidone polymer with an aliphatic aldehyde or ketonebisulfite/hydroquinone developer containing alkylene oxide units is described. The process results in a steeper gradation and consequently improved dot sharpness of the screen image. Additionally, a broader development time interval wherein reproducible dot screen images is obtained.

United States Patent Inventors Joseph LouisDe Munck Kalmthout; Raymond Leopold Florens, Edegem, both of Belgium Appl. No. 668,686

Filed Sept. 18, 1967 Patented Nov. 2, 1971 Assignee Gevaert-Agia,N.V.

Mortsel, Belgium Priority Nov. 19, 1966 Great Britain 41,638/66 DEVELOPMENT PROCESS FOR LlTH-TYPE EMULSION WITH N-VINYL Z-PYRROLIDONE POLYMER [56] References Cited UNITED STATES PATENTS 3,162,534 12/1964 Powers et al 96/63 3,312,553 4/1967 Dersch Fritz 96/107 FOREIGN PATENTS 851,774 10/1960 Great Britain Primary Examiner-Norman G. Torchin Assistant Examiner-John L. Goodrow Attorneys-Robert F. Conrad and Alfred W. Breiner reproducible dot screen images is obtained.

DEVELOPMENT PROCESS FOR LlTH-TYPE EMULSION WITH N-VINYL Z-PYRROLIDONE POLYMER This invention relates to an improved technique for developing light-sensitive silver halide materials.

It is known that the development of continuous tone images by means of a hydroquinone/p-N-methylaminophenol developer is accelerated under the influence of polyoxyalkylene compounds having a molecular weight preferably above 1500. When, however, such polyoxyalkylene compounds are used in combination with a formaldehyde bisulphite/hydroquinone developer, as known from the published German Pat. application No. 1,141,531, an increase of the gradation together with a restrainment of the development rate is obtained. The latter developer combination is found to be very suitable for the development of light-sensitive silver halide materials suitable for use in the graphic art on account of the very contrasty development obtained therewith. As

light-sensitive materials for the reproduction of graphic line or screen images, so-called lith-emulsions of the silver chloride, silver chlorobromide, or silver chlorobromoiodide type (normally less than 1 mole percent of iodide) are generally employed.

It has been found now that very contrasty silver imagescanbe obtained in lith-emulsions of the negative type owing toan' increase in gradation by carrying out the development of said materials in the presence of a N-vinyl-2-pyrrolidone polymer including the latter polymer complexed' with iodine. by means of a developing solution comprising a polymer containing alkylene oxide units, a bisulphite-addition compound of an aliphatic aldehyde or ketone, e.g. formaldehyde bisulfite, and hydroquinone as the sole developing substance.

It has not been possible to detect any chemical interaction between both types of polymeric compounds so that it appears that said compounds exhibit a synergetic activity. By the term negative silver halide emulsion a silver halide emulsion is understood wherein by exposure a latent image is formed in the exposed areas, so a silver halide emulsion of the negative type.

According to a preferred embodiment the development technique of the present invention is applied in combination with silver chloride, silver chlorobromide or silver chlorobromoiodide emulsions (containing at most 50 mole percent of bromide) used for the reproduction of screen images. Here the development yields screen prints with very sharp screen dots and can take place within a broad interval of time without doing harm to the image quality.

It was not obvious that poly(N-vinyl-Z-pyrrolidone) would retard the development in a hydroquinone-formaldehydebisulphite developer since from the United Kingdom Pat. specification No. 851,774 poly(N-vinyl-2-pyrrolidone) wasknown to increase the speed when' used alone in photographic emulsions developed in a N-methyl-p-hydroxyphenyl ammonium sulphate/hydroquinone developer.

The term N-vinyl-Z-pyrrolido'ne polymer when used in the present invention includes the homopolymer and copolymers of N-vinyI-Z-pyrrolidone as well as their iodine complexes. These complexes are addition complexes (addition by inclusion) of molecular iodine with the N-vinyl-2-pyrrolidone polymer. The N-vinyl-2-pyrrolidone polymers may be of high as well as of low molecular weight, however, a molecular weight between 300 and 90,000 being preferred.

Poly(N-vinyl-2-pyrrolidone) suitable for use in the present invention is marketed e.g. under the trade name LUVISKOL by Badische Anilin & Soda-Fabrik, Ludwigshafen, W.-Germany and under the name of PVP, type NP nonpharmaceutical) by General Aniline & Film Corporation, New York, N.Y., U.S.A. The said polymer is available in viscosities of K-20, K-30, K-40 and K-90.

As copolymers of N-vinyl-2-pyrrolidone are used: those of the water-soluble type and containing preferably at least 50 mole percent of N-vinyl-2-pyrrolidone' units. Examples of such copolymers are copoly(vinyl acetate/N-vinyl-2-pyrrolidone) (30/70) and copoly(sodium acrylate/N-vinyl-2-pyrrolidone) (45/55). It is self-explanatory that for obtaining a result equal to that obtained with the homopolymer, a greater amount of copolymer has to be used.

Examples of suitable polymers containing alkylene oxide units are those derived from ethylene oxide and mixtures of ethylene oxide and propylene oxide or butylene oxide with the proviso that said compounds are soluble in water or an alkaline aqueous solution such as an alkaline developing bath.

Preferably water-soluble polymers containing alkylene oxide units and having a molecular weight of at least 1 ,500 are used.

The preparation of alkylene glycol polymers, known as polyalkylene glycols, is described e.g. in Ellis, The Chemistry of Synthetic Resins 1935) pages990 to 994. See therefor also the US. Pat. specification Nos. 1,970,578-2,240,470 and 2,423,549. Their use as sensitizers for silver halide emulsions is described in the United Kingdom Pat. specification No. 600,058 and United-States Pat. specificationN'o. 2,441,389.

Further examples are the'condensation products of alkylene oxides with organic compounds, which contain an active hydrogen atom and are soluble in the alkaline developing bath. in this respect reference can be made to the United Kingdom Pat. specification Nos. 871,801 and 991,608 and to the published German Pat. application No. 1,188,439.

Still further examples are the polymeric compounds cont-ainingoxyalkylene units as described in the United Kingdom Pat. specification Nos. 920,637-945,340 949,643-940,051 and 1,015,023, in the United States Pat. specification No. 3,307,948, in the published Dutch Pat. application Nos. 6,709,016 and 6,612,597, in the published German Pat. application No. 1,141,531 as well as the products containing amino-alkylene and oxyalkylene units described in our US. Pat. application No. 659,334 and in the published Dutch Pat. application No'..6'-,6l4,230.

The N-vinyl-2-pyrrolidone polymer of use according to the present invention is preferably incorporated into-the light-sensitive emulsion layer but may also be incorporated into a watenpermeable' layer under or on top of the emulsion layer, which water-permeable layer stands in water-permeable relationship with the" emulsion layer.-

Preferably the N'-vinyl-2-pyrrolidone polymer is added to the negative light-sensitive silver halide lith-emulsion in dissolved form: in water or a mixture of water and water-miscible organic solvents, which do not impair the photographic characteristics of the emulsion.

However, the said polymer can also be incorporated into the emulsion by inhibition by treating it with a solution containing the polymer.

The N-vinyl'-2-'pyrrolidone polymer used according to the present invention can be added to the light-sensitive silver halide emulsion during different preparation steps of the lightsensitive material. Preferably, however, it is added to the emulsion of the negative type after the chemical ripening.

The optimum. amount of the N-vinyl-2-pyrrolidone polymer to be added to the emulsion depends on the nature of the colloid binder of the silver halide grains, on the amount and type of silver halide in the emulsion, and the stage of addition, since, when adding the N-vinyl-2-pyrrolidone polymer before washing of the emulsion, relatively greater amounts are required.

In general, the N-vinyl-Z-pyrrolidone polymer is present in the light-sensitive material in an amount of 10 mg. to 14 g. per mole of silver halide, but for best results it is preferably present therein in an amount of 10 mg. to 1 g. per mole of silver halide.

When present in the developing bath the N-vinylpyr rolidone polymer is preferably contained therein in an amount of 10 mg. to 10g. per litre.

According to' the characteristics required for the negative silver halide emulsion, the N-vinyLZ-pyrrolidone polymer can be used in the photographic material in combination with spectral sensitizing agents and chemical sensitizing agents such as sulfur-containing compounds, e.g., allyl isothiocyanate, allyl thiourea of sodium thiosulphate, reducing wherein:

each of R and R represents a hydrogen atom, an alkyl, an aralkyl, or an aryl radical, and R represents a hydrogen atom, an alkyl, a carboxyl or an alkoxy carbonyl group.

a color temperature of 3700" K. The exposure was regulated so that the wedge print of the screen embraces the beginning of dot formation as well as the disappearance of the high lights.

The development was performed at 20 C. in a developing bath having the following composition:

' sodium bisulphite 1.5 g. hydroquinone 17.0 g. anhydrous sodium carbonate 60.0 g. anhydrous sodium bicarbonate 8- potassium bromide 10 g. the oxyethylene units containing polycondensation product prepared as described in preparation 2 of the U.K. Pat, specification No.

920,637 0.5 g. water till l,00010 cc.

The developer containing said polycondensation product comprising oxyethylene units is marked in table 1 with P. The developer without that product isr narked with N.

The appreciation of the dot definition occurs visually by comparison with I standard materials which in decreasing order of dot defimtion quality are 1nd1cated with the numbers 1, 2, 3 and 4.

The speed is expressed procentually in respect of the blank which is given the value 100. The speed values compared are those corresponding with a density 3 above fog.

The following example illustrate the present invention without however limiting it thereto.

EXAMPLE A green-sensitized silver chlorobromide emulsion mole percent of bromide) containing 5-methyl-7-hydroxy-striazolo-(1,5-a)-pyrimidine and cadmium chloride as stabilizing agents was divided in aliquot portions after ripening and addition of the necessary coating aids. To the different portions the polymers mentioned in table 1 were added. In that table polymer A is LUVISKOL K 30 (registered trade name for a poly(N-vinyl-pyrrolidone) and polymer B is the reaction product of preparation 3 of the U.K. Pat. application No. 42,590/65. The differently treated emulsion portions were coated in the same way on a cellulose triacetate support.

The light-sensitive material was exposed through a continuous wedge and a glass screen by means ofa light source having Amount 01 polymer Gamma value Speed value (A,lB) per after a developing time 01- nl'ter a developing time 01- mo e of Light-sensitive silver ha- Devel- 2. 5 3 3. 5 4 2. 5 3 3. 5 4 material llde in mg. opcr min. min. min. min. min. min. min. min.

1 11. 5 2 8.575 8. 8 87 193 96 100 1.8 1 .1; s. 8.5 78 15 110 111) N 10. 4 10. 8 12. 5 6. 9 31 5!) P 11. 4 12.8 11. 9 6. 6 71 157 141 N El. 0 8. 6 G. 8 5. 8 68 113 103 103 l 7. 8 l3. 1 11. (i 15. 4 20 50 73 115 N 12.1 10. 3 11. 7 8. 3 311 55 100 107 Further are to be mentioned sensitizing and stabilizing cad- 45 mium salts which may be used in the light-sensitive material as Amount Of n th d 1 er polymer Dot delmitio i after a we as 1n e eve op (A313) per development time 01- Other in redients such as hardenin a ents wettin a ents m0 9 of h g g g Light-sensitive silver ha- Devel- 2.5 3 3.5 4 ydrophilic colloids, latlces and plast1c1zers, can be 1ncor- 50 material lide in mg, mm. min, mm porated into the emulsion in the usual way. 0 3 3 5 4 As antioxydant in the developing composition formal- 5 3 3 dehyde bisulfite is preferred. In the developing composition 1 '3 the polymer containing oxyalkylene groups is preferably used 2 2.5 3 4 in a range of 100 mg. to 10 g. per liter. 2 1 1 The aliphatic aldehyde or ketone bisulphite/hydroquinone 3 developer may further comprise the usual ingredients for a 1 1.5 1 1 lith-developer such as potassium bromide and alkali metal 1 1 5 1 5 borates and carbonates such as sodium carbonate.

We claim:

1. Process for developing a light-sensitive silver halide photographic material containing a negative silver halide emulsion layer of the lith type, which comprises the step of developing said material in the presence of a N-vinyl-Z-pyrrolidone polymer by means of an aliphatic aldehydeor vinyl-2-pyrrolidone polymer homopolymer.

3. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the N- vinyl-2-pyrrolidone polymer is a copolymer containing at least 50 percent of N-vinyl-2-pyrrolidone units and recurring units selected from the group comprising vinyl acetate or sodium acrylate.

4. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein said N- vinyl-2-pyrrolidone polymer has been complexed with iodine.

5. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the negative silver halide emulsion layer of the lith type is a silver chloride emulsion layer, a silver chlorobromide emulsion layer or a silver chlorobromoiodide emulsion layer the latter emulsion layers containing at most 50 mole percent of silver bromide and the silver iodide content of said emulsion layers not surpassing 1 mole percent.

6. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the is a N-vinyl-2-pyrrolidone development is carried out in the presence of a poly(N-vinyl- 2-pyrrolidone) polymer incorporated in the emulsion layer in an amount of 10 mg. to 14 g. per mole of silver halide.

7. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the development is carried out with the said developing solution containing the polymer comprising alkylene oxide units in an amount of mg. to 10 g. per liter.

8. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein during the development a N-vinyl-2-pyrrolidone polymer is present in the emulsion layer in an amount of 10 mg. to l g. and a polymer containing alkylene oxide units is present in a hydroquinone/formaldehyde bisulfite containing developing bath suitable for developing silver halide emulsions for graphic reproductions.

9. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the development is carried out in the presence of a N-vinyl-2-pyrrolidone polymer incorporated in the developing bath. 

2. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the N-vinyl-2-pyrrolidone polymer is a N-vinyl-2-pyrrolidone homopolymer.
 3. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the N-vinyl-2-pyrrolidone polymer is a copolymer containing at least 50 percent of N-vinyl-2-pyrrolidone units and recurring units selected from the group comprising vinyl acetate or sodium acrylate.
 4. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein said N-vinyl-2-pyrrolidone polymer has been complexed with iodine.
 5. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the negative silver halide emulsion layer of the lith type is a silver chloride emulsion layer, a silver chlorobromide emulsion layer or a silver chlorobromoiodide emulsion layer the latter emulsion layers containing at most 50 mole percent of silver bromide and the silver iodide content of said emulsion layers not surpassing 1 mole percent.
 6. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the development is carried out in the presence of a poly(N-vinyl-2-pyrrolidone) polymer incorporated in the emulsion layer in an amount of 10 mg. to 14 g. per mole of silver halide.
 7. Process for developing a light-sensitive silver haLide photographic material according to claim 1, wherein the development is carried out with the said developing solution containing the polymer comprising alkylene oxide units in an amount of 100 mg. to 10 g. per liter.
 8. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein during the development a N-vinyl-2-pyrrolidone polymer is present in the emulsion layer in an amount of 10 mg. to 1 g. and a polymer containing alkylene oxide units is present in a hydroquinone/formaldehyde bisulfite containing developing bath suitable for developing silver halide emulsions for graphic reproductions.
 9. Process for developing a light-sensitive silver halide photographic material according to claim 1, wherein the development is carried out in the presence of a N-vinyl-2-pyrrolidone polymer incorporated in the developing bath. 